The invention relates to a method of increasing the signal-to-noise ratio of a periodical electrical signal and to a circuit arrangement for carrying out this method.
Several methods of increasing the signal-to-noise ratio are generally known already. For example, in one method for processing back-scattering signals in light wave guides, successive back-scattering signals are recorded by a rapid digital transient recorder. Then, by means of a digital computer, average values are formed from the successive back-scattering signals for the same portions of each successive signal. This digital processing permits a very effective noise suppression. However, to obtain an improvement of the signal-to-noise ratio by a factor M requires M.sup.2 back-scattering signals for averaging. Other disadvantages of this method reside in the high cost for the rapid digital transient recorder and in the relatively complicated digital processing required.
German published patent application No. 31 25 140 discloses an analogue method of improving the signal-to-noise ratio of a back-scattering signal in lightwave guides. In the method disclosed therein, the back-scattering signals are successively added to the previously stored signal by using an analogue storage chain. Each stored back-scattering signal or, alternatively, the variation of its curve, is read out with an appropriate time delay so that the stored signal is pointwise added at the correct instant to a successive back-scattering signal, and the resulting signal is written back into the analogue storage chain. In this kind of averaging, a desired improvement of the signal-to-noise ratio by the factor M also requires M.sup.2 back-scattering signals.